1. Field of the Invention
This invention relates to an improved gate valve that prevents the seats from sticking or becoming distorted by remaining firmly sealed, whether the valve is in the open-flow or closed-flow position. The present invention is typically utilized in pipelines like those in power plants where pulverized coal traverses to a boiler. Previous to this invention, the pulverized coal would back into portions of the gate valve and/or the slots where it rested causing same to malfunction. The present invention indicates two sections of body and two sections of gate which join together. Inside the gate section, there is a wedge-shaped part with rollers for easy sliding which is connected to a driving mechanism.
2. Description of the Prior Art
Previous gate valves like Doster U.S. Pat. No. 2,711,877, however effective, allow the medium which may be a fluid, gas, ash, or other type of solid to enter into various parts of the mechanism causing the valve to frequently stick. Doster is a typical gate valve utilizing a conduit member which aligns with the inlet and outlet ports for an open-flow position. However, in the process of opening and closing the gate, the medium readily seeps into the rollers and other parts requiring continued maintenance and creating an unsafe and hazardous condition.
A second example is Wheatley U.S. Pat. No. 4,314,579 which also uses typical components including a conduit, inlet and outlet ports and a valve seat located on the upstream side of the gate. It also encounters the same type of problems as Doster.
Erwin U.S. Pat. No. 4,405,113 utilizes a valve body consisting of three (3) sections with the intermediate section including a gate chamber in which a gate is placed and controlled through a drive stem member. Erwin also uses camming surfaces in cooperation with rollers to place outward forces on the seal. The typical gate conduit aligns with flow passageways in the valve body permitting the necessary flow.
Doster, Wheatley and Erwin all disclose slide gate valves in which the gate is formed in two sections or more. Doster and Wheatley use a wedge and Doster and Erwin use rollers. However, construction of these prior patents is more complex and thus more expensive to produce, yet the valves do not work as smoothly, effectively and do not provide the necessary protection to the inner-working mechanism of the gate.
U.S. Pat. Bohnhardt No. 1,803,889, Knox No. 2,952,437 and Husted No. 4,573,660 are of general interest and indicate typical gate valves.